1. Field
The disclosure relates generally to a method and apparatus for installing fluid fittings and fasteners. More particularly, the present disclosure relates to a self-contained, combined wrench and marking system for installing and marking fluid fittings and fasteners, and to a method for installing and marking fluid fittings and fasteners.
2. Background
An aircraft includes many movable structures, for example and without limitation, wing flaps, vertical fins and ailerons, that are operated hydraulically. Accordingly, a typical aircraft may include many hydraulic lines that extend throughout the aircraft and that are comprised of numerous line sections joined together by fluid fittings.
The fittings are assembled to the line sections using nuts, and it is important that the assembled structures be fluid-tight. In a typical procedure for installing a hydraulic line in an aircraft, a mechanic first loosely attaches one end of a fitting to a line section by hand-tightening the nut at the one end of the fitting, then stretches or compresses the line section so that the opposite end of the fitting can be attached to another line section, again by hand-tightening the nut at the opposite end of the fitting. The mechanic then further tightens the nuts, first at one end and then at the opposite end of the fitting. This process of alternately tightening the nuts at the ends of the fitting may be repeated two or three times until the nuts at both ends of the fitting are fully tightened.
A mechanic may install several hundred hydraulic fittings in a day, and to help ensure that all nuts and fittings have been properly tightened, it is often the practice to mark a nut and/or fitting after it has been fully tightened.
As a result of the process of alternately and repeatedly tightening the nuts at the opposite ends of a fitting, however, it is not uncommon that the mechanic might inadvertently fail to fully tighten the nut at one or both ends of a fitting, yet still mark the nuts as being fully tightened.
All fittings in a hydraulic line of an aircraft are subjected to leak-testing such that any nuts that may have been only hand-tightened or that were otherwise improperly installed will be identified and properly fastened. When a fitting fails leak-testing, however, it is necessary to clean the leaked aviation hydraulic fluid (e.g., Skydrol) from surrounding surfaces, and to then fully tighten any loose nuts prior to retesting of the fitting. In addition to being time consuming, the preferred cleaning agent used to clean the leaked aviation hydraulic fluid is Freon which is a hazardous material and may also cause damage to the surrounding surfaces that requires repair.
Thus, it would be desirable to minimize the number of fittings that fail during leak-testing.
The typical procedure for marking an assembled hydraulic joint requires the mechanic to apply a colored compound, (e.g., Inspection seal lacquer F925) by squeezing a small tube so that a stripe of the compound, sometimes referred to as a “torque stripe”, covers both the fitting and the nut. This procedure for marking an installed hydraulic joint may be unsatisfactory.
One problem, as indicated above, is that the mechanic may inadvertently mark a fitting that has not been fully tightened. Also, these manual marking procedures are time consuming and reduce productivity. Recognizing the inadequacies of manual marking procedures, a marking wrench was developed. The prior art marking wrench both tightens a fastener and then marks the tightened nut with ink to indicate that the nut has been tightened.
The prior art marking wrench, however, is still not fully satisfactory. For one thing, the marking wrench only marks the nut and not its mating fitting. It is desirable to have the mark cover both nut and fitting so that it would be known if someone loosened, or tampered with the nut. A misaligned mark on the nut and fitting surfaces flags this condition. The prior art marking wrench is also non-ratcheting which makes operation of the wrench rather slow. Furthermore, the prior art marking wrench contacts the nut with ink impregnated felt, but trials of this wrench found that the felt dried up, rendering its marking capability useless.
There is, accordingly, a need for a mechanism for installing fittings and fasteners in hydraulic lines in an aircraft and in other applications that will minimize fluid leaks during leak-testing, and that will also automatically mark installed fittings and fasteners after they have been properly installed.